Treating wood and preventing corrosion of cables



Feb. 7, 1933. R, M BURNS 1,896,478

TREATING WOOD AND PREVENTING CORROSION OF CABLES Filed Aug. 18, 1928:ars-.5.7.

/N VEN TUR /oERr M. Bun/vs A TTR/VEV Patented Feb. 7, 1933 UNITED STATESPATENT l ori-ucr.

ROBERT M. BURNS, F BROOKLYN, NEW YORK, ABSIGNOR TO BELL TELEPHONE LABO-RATORIES, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORKTREATING WOOD AND PREVENTING CORROSION OF CABLES Application led August18, .1928. Serial No. 300,545.

This invention relates to a method of treatin conduits and cablescontained therein. A

primary object of the invention is to prevent corrosion of sheathings ofsignaling cables '-5 laid in conduits.

A further object is to so treat conduits as to put them into a conditionsuch that cables laid therein at the time, or to be laid afterwards7will not be corroded.

Large amounts of wooden ducts are employed in various parts of thecountry as containers for lead and lead-alloy covered telephone cables.In the case of certain of these a serious problem arose by virtue of thefact that the cable sheaths were becoming corroded to the extent ofcausingfaults therein leading to failures in the conductors and othertroubles.

Researches disclosed the fact that the corrosion was occurringprincipally in conduits made of Douglas fir (especially when not wellseasoned) treated-before layingwith creosote by a process in which thewood is immersed in creosote oil and subjected to a minimum vacuum of 20of mercury and to temeratures ranging between 190 F. and 200 EY untilthe moisture contained became reduced to approximately the libresaturation point, after which pressure was applied until the timber hadabsorbed a sufficient amount of creosote oil, after which the pressurewas removed and the retorts emptied of preservative and subjected to avacuum of 20 of mercury for about two hours under an average temperatureof 160 F. Theory and investigation indicate that the temperaturesincident to impregnation may increase the acidic content of the wood.

However, the purposes and objects of the invention are not limited tothe treatment of .45 After extensive investigations and a chemicalexamination of the atmosphere contained in the corrosive conduits it wasinferred that the corrosion resulted from a chemical reaction involvingvolatile organic acids. It is supposedthat these acids are derived fromI ammonia gas through the affected conduit.

A suitable apparatus vfor this purpose con- Sisted of a large capacityblower o rated by a gasoline engine, a mixing tan with necessaryconnections and an outlet through a manifold for distributing themixture of air and ammonia to the ducts. A tank of liquid ammonia wasconnected to the mixing "ta-nk through a flow meter. For mobility theentire apparatus was mounted on a motordriven truck. The air-ammoniamixture lfound most suitable contained about 2% ammonia ,and this wasused in Atreating a large amount of the affected creosoted wood conduit.'Other percentages of ammonia will produce the desired results. Theresult of the treatment as so far observed has been that the trouble dueto corrosion has practically ceased. In any case it is deemed that oneor more retreatments will suice to correct the corrosive condition ineven the most badly affected conduits.

It is believed that the corrosion results from the interaction ofaccumulations of acetic acid or equivalent acids with oxygen, carbondioxide `and Water vapor upon the duit ducts already containing cablesand lead. The chemical reaction involved is believed to be the same asthat involved in the production of white lead. This reaction consistsinthe formation of lead acetate by the action of acetic acid and oxygenon lead and the conversion of this product into a basic lead carbonatewith accompanying liberation of acetic acid which then repeats theprocess cyclically. The ammonia gas is thought to act by neutralizingthe acetic acid with resultant formation of ammonium Y acetate, anon-voltatile salt.

Apparatus for practicing the invention is Vshown in the drawing in whichFiga'l discloses a completeV system and Figs.' 2 and 3 details ofsealing the ammonia supplying hose connectioninto conduits.

In Fig. 1 the conduits l containing cables 2 are supplied withgas'through the hose 3. ,Ammonia gas stored under pressure in a tank 4passes through valve 5 into a mixing tank vwhereit is mixed with airsupplied through lthe blower Y' by gas engine 8.V 'This apparatus isdisclosed in a purely diagrammatic manner with omissionof the details ofpressure measuring and flowY measuring de-V "v1ces,etc. A n Y Fig. 2shows a form of nozzle 9 for use in treating conduit containing cable.The

nozzle is sealed into the conduitwith wax or other suitable substance10.

y In Fig. 3 no special nozzle isnecessary and Vthe hoserconnection issealed directly into the conduit with the wax. v

The treatment is equally applicable to conthose into which cables havenot yet been drawn. It is deemed that the method' is applicable to anyconduit system in which corrosion'occurs as a result of anaccumula yftio'n ofco'rrosive acids;

'Y A modified method' has been used to treat conduit was: placed'inretorts and the retorts iilled with ammonia.

, A further modieea method is to da to the regularvstock creosote oil,used to impregsuficient, amount of coal tar' bases to neutralize theacids of the treated wood. Coal tar bases, as here referred to, arebasic subvconduit'before laying. After'cresoting the i nate the conduit,a quantity of ammonia or a stances occurring in coal tar, bone tar orsimilar substances which can be separated by methods well-known. What isclaimed is:

. l. The method of treating underground conduits containing or designedto contain cables sheathed with lead'compositions and also containingVsubstances promoting deterioration ofthe sheath for the purpose ofpreventing deterioration. of the sheath by corrosion which comprisespassing ammonia gas through the conduit.V

between the lead sheath and corroding agents 2. The method ofV'preventing interaction l

